1. Field of the Invention
This invention concerns tubing cut-off apparatus of the type used to sever continuously emanating lengths of tubing or other elongated stock continuously emanating from a mill in which the cut-off apparatus includes a cut-off die set operated by a swinging ram, which die set is caused to be clamped to the tubing during the severing operations in the apparatus, the severing of the tubing being carried out by a vertically reciprocating cut-off blade. More particularly, the present invention is drawn to an improvement in the notching mechanism which has been utilized in the past in conjunction with such cut-off die sets to notch the upper periphery of the tubing just prior to severing by the main cut-off blade. This eliminates the need for subsequent reshaping of the tube to eliminate dimpling which tends to occur in the absence of such pre-notching.
2. Description of the Prior Art
In cut-off die sets of the type described above, there is often included a pre-notching mechanism in which a notching blade is reciprocated across the upper periphery of the tubing after the tubing is clamped within the die set clamping jaws and just prior to descent of the main cut-off blade. The pre-notching eliminates the cusping or dimpling of the tubing to a large extent to the point that subsequent reshaping of the tubing ends of the severed length of tubing will not be normally required. While this expedient does accomplish its intended purpose, the designs heretofore used have certain weaknesses. Firstly, the mechanism operates by reciprocating the notching blade to and fro across the upper periphery of the tubing just prior to descent of the main cut-off blade. Since only a short time interval is available during which the tubing is clamped within the die set and since the notching blade must be removed from the path of the descending main cut-off blade, the movement of the notching blade is necessarily very rapid. These mechanism have in the past involved the use of cams and cam followers to obtain the reciprocal movement and this very rapid movement has contributed in no small part to the rate of wear of these cam mechanisms. In addition, these rapid part velocities have a tendency to create failures of parts due to the shock loading and the high stress levels which may result.
A further problem is created by the high velocity of the notching blade inasmuch as this creates considerable heating of the notching blade, in turn leading to relatively rapid wear thereof.
The blade wear problem is further excacerbated by the situation which requires the notching blade to first traverse the tubing during the notching operation and then to be withdrawn across the upper surface of the tube periphery. During the notching stroke, the forces involved necessarily produced substantial deflection of the tubing and blade such that a sufficient clearance space is not created by the notching operation so as to allow drag free withdrawal of the notching blade. That is, as the blade withdraws, the deflection forces involved having been relieved, the tubing relaxes reducing the clearance space so as to create drag forces between the tubing notch and the notching blade, as it returns, thus further contributing to power losses in the machine, as well as the further degredation in blade life. In addition the high part velocities involve the respective parts increases the sizing of the parts required, bearing design specifications, etc., increasing the manufacturing cost of the mechanism.
Accordingly, it is an object of the present invention to provide a cut-off die set of the sort described including a tube notching mechanism which increases the cycle time available for notching operation of the mechanism.
It is a further object of the present invention to provide such a cut-off die set in which the notching blade velocity during the notching pass is substantially reduced over the designs heretofore utilized.
It is yet another object of the present invention to provide a notching mechanism which eliminates the blade withdrawal drag to further enhance blade wear life.
It is still a further object of the present invention to provide a notching mechanism therefore which operates at substantially reduced part velocities to thereby decrease the wear on the operating mechanism and also reduce the failure rate of the notching blade operating mechanism.